Prompted by one of their number, who had previously indulged, five mature thirty-something couples, who had been friends for years and collectively known as 'the Group', decide to indulge in some novel partner swapping. At first everything appears fine and the couples believe that nothing has changed between them and that their relationships are safe. However, everything is not fine and petty jealousies start to arise, as some members perceive that others are benefiting more from the arrangement than themselves. The tensions mount and deeper, darker secrets begin to reveal themselves, especially when one member of the group changes her partner. Eventually, the tension and jealousy proves too much with catastrophic results for the marriages and friendship of the group.